The problem with local, less aggressive measures is that people act in their self interest to bypass them for convenience or safety, and they make the problem worse. Recent examples:

- Lockdown in northern Italy: People ran to the south taking the virus with them. - Schools closing, folks asked to work from home in Madrid: Families drive to the coast where bars and restaurants are full.

I agree that in a place where compliance with social distance measures is high (I'm thinking South Korea, Japan), that would be enough. But that doesn't work everywhere.